摘要
28.1. Introduction The energy content in radiation from beyond our Galaxy is dominated by the cosmic microwave background （CMB）, discovered in 1965 [1]. The spectrum of the CMB is well described by a blackbody function with T = 2.7255 K. This spectral form is a main supporting pillar of the hot Big Bang model for the Universe. The lack of any observed deviations from a blackbody spectrum constrains physical processes over cosmic history at redshifts z ≤ 107 （see earlier versions of this review）.
28.1. Introduction The energy content in radiation from beyond our Galaxy is dominated by the cosmic microwave background （CMB）, discovered in 1965 [1]. The spectrum of the CMB is well described by a blackbody function with T = 2.7255 K. This spectral form is a main supporting pillar of the hot Big Bang model for the Universe. The lack of any observed deviations from a blackbody spectrum constrains physical processes over cosmic history at redshifts z ≤ 107 （see earlier versions of this review）.
